A Fox News reporter is under investigation by the Federal Bureau of Investigation over allegations of conspiracy that resulted from a leak of classified material from a State Department source.

During the investigation of State Department adviser Stephen Kim, law enforcement officials obtained a search warrant for some private emails of James Rosen, the chief Washington correspondent for Fox News. Investigators also tracked Rosen's comings and goings from the State Department.

“The Reporter did not possess a security clearance and was not entitled to receive the information published in the June 2009,” wrote FBI Special Agent Reginald Reyes. “Nor was Mr. Kim authorized, directly or indirectly, by the United States Government to deliver, communicate, or transmit the TS/SCI information in the article to the Reporter or any other member of the press.”

Even if the press reports classified stuff that is not all that important it sends a message to foreign countries that the U.S. can’t be trusted.

- Robert Glover, University of Virginia

In June 2009, Rosen reported that U.S. intelligence officials warned President Barack Obama and senior U.S. officials that North Korea would respond to a United Nations Security Council resolution condemning nuclear tests with another nuclear test.

The lengthy 2010 affidavit for a search warrant, first reported by The Washington Post, does not identify Rosen as "the reporter," but he wrote the story at issue, and Fox News confirmed it was him on Monday.

"We are outraged to learn today that James Rosen was named a criminal co-conspirator for simply doing his job as a reporter," said Michael Clemente, Fox's executive vice president for news. "In fact, it is downright chilling. We will unequivocally defend his right to operate as a member of what up until now has always been a free press."

Reyes’ affidavit goes into detail about a number of phone calls and emails between Rosen and Kim before the article in question was published. In the emails exchanges, the two used code names to mask their identities, Kim was “Alex,” Rosen was “Leo.”

“Thanks Leo… Let’s break some news, and expose muddle-headed policy when we see it – or force the administration's hand to go in the right direction, if possible,” Kim wrote in a May 22, 2009 email, according to the affidavit.

What makes this case different from the Obama administration secretly subpoenaed the Associated Press’ phone records is that Rosen is a possible target for prosecution. Reyes wrote that Rosen may have committed a "conspiracy to violate" a section of a law against leaking classified info, which he wrote was "punishable by up to 10 years imprisonment."

"Because of the Reporter's own potential criminal liability in this matter, we believe that requesting the voluntary production of the materials from Reporter would be futile and would pose a substantial threat to the integrity of the investigation and of the evidence we seek to obtain by the warrant," Reyes added.

The White House wouldn't comment about tracking Rosen, citing an ongoing criminal investigation. Instead, White House spokesman Jay Carney cited a media shield law Obama supports as evidence of his commitment to journalistic freedom, reprising an argument the White House used a week earlier in declining to address the Justice Department's probe involving AP.

"The president believes it's important that we find a proper balance between a need — absolute need — to protect our secrets and to prevent leaks that can jeopardize the lives of Americans and can jeopardize our national security interests on the one hand, and the need to defend the First Amendment and protect the ability of reporters to pursue investigative journalism," Carney said.

Along with Fox News, a number of journalists and freedom of press groups have backed Rosen’s work and stated their alarm at the scrutiny he has received.

"U.S. government efforts to prosecute leakers by obtaining information from journalists has a chilling effect domestically and sends a terrible message to journalists around the world who are fighting to resist government intrusion," said Joel Simon, executive director of the Committee to Protect Journalists.

While the government has recently received a great deal of criticism for the purported crackdown on journalists, some policy makers and academics argue that the recent string of unveiled security leaks has a negative impact on the U.S.’s foreign policy and will lead other countries to not trust government agencies with sensitive information.

“Even if the press reports classified stuff that is not all that important, it sends a message to foreign countries that the U.S. can’t be trusted,” Robert Turner, the associate director for the University of Virginia’s Center or National Security Law, told Fox News Latino.